What is a series/promotional recruitment?

Applications are accepted only for jobs open for recruitment. County of San Diego has two types of recruitments:

Series Recruitment - a type of recruitment where applications are accepted at intervals as employment needs require and names are placed on one employment list in order of final grades regardless of dates of application. Applicants may be accepted only once under each recruitment number.

Promotional Recruitment - limited to employees in the County service who received their appointment from an employment list, to individuals on County reinstatement lists, employees on authorized leave of absence, or to individuals on re-employment lists as a result of County lay-off. Applicants who terminate County employment will no longer be eligible pursuant to Civil Service Rule 2.1.6(k).